Sec Form 4 Filing - Christianson Gary @ Cascadian Therapeutics, Inc. - 2018-03-09

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Christianson Gary 2. Issuer Name and Ticker or Trading Symbol Cascadian Therapeutics, Inc. [ CASC] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) Chief Operating Officer (Last) (First) (Middle) C/O CASCADIAN THERAPEUTICS, INC., 3101 WESTERN AVE., SUITE 600 3. Date of Earliest Transaction (MM/DD/YY) 03/09/2018 (Street) SEATTLE, WA98121 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 03/09/2018 U 6,515 D 0 D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Stock Option (Right to buy) $ 19.92 03/09/2018 D 8,334 ( 2 ) 12/01/2018 Common Stock 8,334 ( 3 ) 0 D Stock Option (Right to buy) $ 41.52 03/09/2018 D 8,334 ( 4 ) 12/01/2019 Common Stock 8,334 ( 3 ) 0 D Stock Option (Right to buy) $ 28.44 03/09/2018 D 8,334 ( 5 ) 12/12/2020 Common Stock 8,334 ( 3 ) 0 D Stock Option (Right to buy) $ 10.44 03/09/2018 D 25,000 ( 6 ) 12/12/2021 Common Stock 25,000 ( 3 ) 0 D Stock Option (Right to buy) $ 10.56 03/09/2018 D 16,667 ( 7 ) 12/16/2022 Common Stock 16,667 ( 3 ) 0 D Stock Option (Right to buy) $ 21.06 03/09/2018 D 41,667 ( 8 ) 09/24/2023 Common Stock 41,667 ( 3 ) 0 D Stock Option (Right to buy) $ 6.9 03/09/2018 D 41,667 ( 9 ) 05/17/2024 Common Stock 41,667 ( 10 ) 0 D Stock Option (Right to buy) $ 4.64 03/09/2018 D 51,200 ( 11 ) 01/11/2027 Common Stock 51,200 ( 12 ) 0 D Stock Option (Right to buy) $ 3.99 03/09/2018 D 68,000 ( 13 ) 09/18/2027 Common Stock 68,000 ( 14 ) 0 D Restricted Stock Units ( 15 ) 03/09/2018 D 11,300 ( 16 ) ( 17 ) Common Stock 11,300 ( 15 ) 0 D Restricted Stock Units ( 18 ) 03/09/2018 D 15,000 ( 19 ) ( 17 ) Common Stock 15,000 ( 18 ) 0 D Restricted Stock Units ( 20 ) 03/09/2018 D 164,500 ( 21 ) ( 17 ) Common Stock 164,500 ( 20 ) 0 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Christianson Gary C/O CASCADIAN THERAPEUTICS, INC. 3101 WESTERN AVE., SUITE 600 SEATTLE, WA98121 Chief Operating Officer Signatures /s/ Julia M. Eastland (Attorney-in-Fact) 03/13/2018 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Shares of Common Stock tendered in the tender offer launched by Valley Acquisition Sub, Inc. on February 8, 2018 pursuant to that certain Agreement and Plan of Merger, dated January 30, 2018, among Seattle Genetics, Inc., Valley Acquisition Sub, Inc., and Cascadian Therapeutics, Inc. (the "Merger Agreement"), to acquire all of the outstanding shares of common stock of Cascadian Therapeutics, Inc., par value $0.0001 per share, at a purchase price of $10.00 per share ("Offer Price"), net to the seller in cash, without interest and less any required withholding taxes. ( 2 )25% of the shares subject to the option vest on the first anniversary of the grant date of December 1, 2010, and the remainder vest monthly thereafter for 36 months. ( 3 )Pursuant to the Merger Agreement, the option was cancelled and terminated without payment because the exercise price exceeded the Offer Price. ( 4 )25% of the shares subject to the option vest on the first anniversary of the grant date of December 1, 2011, and the remainder vest monthly thereafter for 36 months. ( 5 )25% of the shares subject to the option vest on the first anniversary of the grant date of December 12, 2012, and the remainder vest monthly thereafter for 36 months. ( 6 )25% of the shares subject to the option vest on the first anniversary of the grant date of December 12, 2013, and the remainder vest monthly thereafter for 36 months. ( 7 )25% of the shares subject to the option vest on the first anniversary of the grant date of December 16, 2014, and the remainder vest monthly thereafter for 36 months. ( 8 )25% of the shares subject to the option vest on the first anniversary of the grant date of September 24, 2015, and the remainder vest monthly thereafter for 36 months. ( 9 )25% of the shares subject to the option vest on the first anniversary of the grant date of May 17, 2016, and the remainder vest monthly thereafter for 36 months. ( 10 )Pursuant to the Merger Agreement, the option was cancelled in exchange for a cash payment of $129,167.70, which represents the product of (a) the difference between $10.00 and the exercise price of the option per share, multiplied by (b) the number of shares subject to the option. ( 11 )25% of the shares subject to the option vest on the first anniversary of the grant date of January 11, 2017, and the remainder vest monthly thereafter for 36 months. ( 12 )Pursuant to the Merger Agreement, the option was cancelled in exchange for a cash payment of $274,432.00, which represents the product of (a) the difference between $10.00 and the exercise price of the option per share, multiplied by (b) the number of shares subject to the option. ( 13 )25% of the shares subject to the option vest on the first anniversary of the grant date of September 18, 2017, and the remainder vest monthly thereafter for 36 months. ( 14 )Pursuant to the Merger Agreement, the option was cancelled in exchange for a cash payment of $408,680.00, which represents the product of (a) the difference between $10.00 and the exercise price of the option per share, multiplied by (b) the number of shares subject to the option. ( 15 )Pursuant to the Merger Agreement, the restricted stock units were cancelled in exchange for a cash payment of $113,000.00, which is the product of the total number of shares subject to such restricted stock unit grant multiplied by the Offer Price. ( 16 )The restricted stock units were granted on January 11, 2017 and 25% of the shares vest on each anniversary of the grant date for four years. ( 17 )The restricted stock units expire upon the earlier of the settlement of the units and the unitholder's termination of service. ( 18 )Pursuant to the Merger Agreement, the restricted stock units were cancelled in exchange for a cash payment of $150,000.00, which is the product of the total number of shares subject to such restricted stock unit grant multiplied by the Offer Price. ( 19 )The restricted stock units were granted on September 18, 2017 and 25% of the shares vest on each anniversary of the grant date for four years. ( 20 )Pursuant to the Merger Agreement, the restricted stock units were cancelled in exchange for a cash payment of $1,645,000.00, which is the product of the total number of shares subject to such restricted stock unit grant multiplied by the Offer Price. ( 21 )The restricted stock units were granted on January 31, 2018 and 25% of the shares vest on each anniversary of the grant date for four years.

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